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Aim: In the present study, we investigated the involvement of NLRP3 inflammasome in the intestinal epithelial barrier (IEB) changes associated with obesity, and its role in the interplay between enteric glia and intestinal epithelial cells (IECs)., Methods: Wild-type C57BL/6J and NLRP3-KO ( -/- ) mice were fed with high-fat diet (HFD) or standard diet for 8 weeks. Colonic IEB integrity and inflammasome activation were assessed. Immunolocalization of colonic mucosal GFAP- and NLRP3-positive cells along with in vitro coculture experiments with enteric glial cells (EGCs) and IECs allowed to investigate the potential link between altered IEB, enteric gliosis, and NLRP3 activation., Results: HFD mice showed increased body weight, altered IEB integrity, increased GFAP-positive glial cells, and NLRP3 inflammasome hyperactivation. HFD-NLRP3 -/- mice showed a lower increase in body weight, an improvement in IEB integrity and an absence of enteric gliosis. Coculture experiments showed that palmitate and lipopolysaccharide contribute to IEB damage and promote enteric gliosis with consequent hyperactivation of enteric glial NLRP3/caspase-1/IL-1β signaling. Enteric glial-derived IL-1β release exacerbates the IEB alterations. Such an effect was abrogated upon incubation with anakinra (IL-1β receptor antagonist) and with conditioned medium derived from silenced-NLRP3 glial cells., Conclusion: HFD intake elicits mucosal enteric gliotic processes characterized by a hyperactivation of NLRP3/caspase-1/IL-1β signaling pathway, that contributes to further exacerbate the disruption of intestinal mucosal barrier integrity. However, we cannot rule out the contribution of NLRP3 inflammasome activation from other cells, such as immune cells, in IEB alterations associated with obesity. Overall, our results suggest that enteric glial NLRP3 inflammasome might represent an interesting molecular target for the development of novel pharmacological approaches aimed at managing the enteric inflammation and intestinal mucosal dysfunctions associated with obesity., (© 2024 The Author(s). Acta Physiologica published by John Wiley & Sons Ltd on behalf of Scandinavian Physiological Society.)

Several studies have provided interesting evidence about the role of the bidirectional communication between the gut and brain in the onset and development of several pathologic conditions, including inflammatory bowel diseases (IBDs), neurodegenerative diseases, and related comorbidities. Indeed, patients with IBD can experience neurologic disorders, including depression and cognitive impairment, besides typical intestinal symptoms. In parallel, patients with neurodegenerative disease, such as Parkinson disease and Alzheimer disease, are often characterized by the occurrence of functional gastrointestinal disorders. In this context, enteric glial cells and brain astrocytes are emerging as pivotal players in the initiation/maintenance of neuroinflammatory responses, which appear to contribute to the alterations of intestinal and neurologic functions observed in patients with IBD and neurodegenerative disorders. The present review was conceived to provide a comprehensive and critical overview of the available knowledge on the morphologic, molecular, and functional changes occurring in the enteric glia and brain astroglia in IBDs and neurologic disorders. In addition, our intent is to identify whether such alterations could represent a common denominator involved in the onset of comorbidities associated with the aforementioned disorders. This might help to identify putative targets useful to develop novel pharmacologic approaches for the therapeutic management of such disturbances., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Ulcerative colitis (UC) is an inflammatory bowel disease with alterations of colonic motility, which influence clinical symptoms. Although morpho-functional abnormalities in the enteric nervous system have been suggested, in UC patients scarce attention has been paid to possible changes in the cells that control colonic motility, including myenteric neurons, glial cells and interstitial cells of Cajal (ICC). This study evaluated the neural-glial components of myenteric ganglia and ICC in the colonic neuromuscular compartment of UC patients by quantitative immunohistochemical analysis. Full-thickness archival samples of the left colon were collected from 10 patients with UC (5 males, 5 females; age range 45-62 years) who underwent elective bowel resection. The colonic neuromuscular compartment was evaluated immunohistochemically in paraffin cross-sections. The distribution and number of neurons, glial cells and ICC were assessed by anti-HuC/D, -S100β and -c-Kit antibodies, respectively. Data were compared with findings on archival samples of normal left colon from 10 sex- and age-matched control patients, who underwent surgery for uncomplicated colon cancer. Compared to controls, patients with UC showed: ( i) reduced density of myenteric HuC/D+ neurons and S100β+ glial cells, with a loss over 61% and 38%, respectively, and increased glial cell/neuron ratio; ( ii) ICC decrease in the whole neuromuscular compartment. The quantitative variations of myenteric neuro-glial cells and ICC indicate considerable alterations of the colonic neuromuscular compartment in the setting of mucosal inflammation associated with UC, and provide a morphological basis for better understanding the motor abnormalities often observed in UC patients. [ABSTRACT FROM AUTHOR]

The analysis of myenteric neurons is becoming increasingly important for the assessment of enteric nervous system injury and degeneration occurring in motor disorders of the gut. Limited information is presently available on the quantitative estimation of myenteric neurons and glial cells in paraffin-embedded colonic sections; additional data would be useful for diagnostic purposes. In this morphometric study, we performed immunohistochemistry to count myenteric neurons and glial cells in paraffin sections of human colon. Serial cross sections of formalin-fixed paraffin-embedded full-thickness normal human left colon ( n = 10, age-range: 50–72 years) were examined. HuC/D and S100β antigens were found to be the best markers for the detection of neurons and glial cells, respectively. Significant correlations were noted between the numbers of neurons/glial cells and the respective myenteric ganglion areas. These findings suggest that HuC/D-S100β-immunostained paraffin cross sections of human colon can be regarded as valuable tools for the quantitative estimation of myenteric neurons and glial cells. Based on the present method, only a limited number of paraffin sections are needed for reliable quantitative assessments of myenteric ganglion cells, thus allowing fast and simple approaches in the settings of the histopathological diagnosis of colonic motility disorders and retrospective evaluations of pathological archival tissue specimens. [ABSTRACT FROM AUTHOR]

Background: Nucleotide-binding oligomerization domain leucine rich repeat and pyrin domain containing protein 3 (NLRP3) inflammasome activation in immune/inflammatory cells contributes to enteric inflammation and bowel dysmotility in obesity (1). However, the involvement of NLRP3 inflammasome in enteric glial activation and gut barrier alterations associated with obesity has not yet been investigated. Aim: This study examined the interplay among enteric glia NLRP3 inflammasome activation and intestinal barrier impairments in high-fat diet (HFD)-induced obesity Methods: Wild-type C57BL/6J mice were fed with HFD or standard diet for 8 weeks. The remodelling of intestinal epithelial barrier in the colonic wall were assessed by standard histological staining, immunohistochemistry and immunofluorescence and western blot. Double-immunofluorescence of ASC and GFAP-positive glial cells was performed to characterize inflammasome activation in enteric glial cells. The molecular mechanisms underlying the interplay between altered intestinal barrier, enteric gliosis and NLRP3 activation in the setting of obesity were investigated with in vitro co-culture experiments enteric glial cells (EGCs) and intestinal epithelial cells (IECs). Results: After 8 weeks of HFD, animals displayed a remodeling of mucus layer, decrease in expression of tight junction proteins along with an increase in proliferating epithelial cells in colonic crypts. HFD animals were also characterized by increased ASC immunopositivity in GFAP-positive glial cells. In co-culture experiments, exposure to palmitate and lipopolysaccharide, besides to induce intestinal epithelial barrier alterations, promotes enteric gliosis with consequent hyperactivation of enteric glial NLRP3/caspase-1/IL-1β signaling pathway. The glial-derived IL-1β release contributes to exacerbate the disruption of IEB. Such an effect was abrogated upon incubation with IL-1β receptor antagonist, anakinra. Conclusions: Glial NLRP3 inflammasome acts as a regulatory hub linking EGCs and IECs, representing a promising therapeutic target for the treatment of gut barrier alterations related to obesity. [ABSTRACT FROM AUTHOR]

Patients with Parkinson's disease (PD) are often characterized by functional gastrointestinal disorders. Such disturbances can occur at all stages of PD and precede the typical motor symptoms of the disease by many years. However, the morphological alterations associated with intestinal disturbances in PD are undetermined. This study examined the remodelling of colonic wall in 6-hydroxydopamine (6-OHDA)-induced PD rats. 8 weeks after 6-OHDA injection animals were sacrificed. Inflammatory infiltrates, collagen deposition and remodelling of intestinal epithelial barrier and tunica muscularis in the colonic wall were assessed by histochemistry, immunohistochemistry, immunofluorescence and western blot analysis. 6-OHDA rats displayed significant alterations of colonic tissues as compared with controls. Signs of mild inflammation (eosinophil infiltration) and a transmural deposition of collagen fibres were observed. Superficial colonic layers were characterized by severe morphological alterations. In particular, lining epithelial cells displayed a reduced claudin-1 and transmembrane 16A/Anoctamin 1 (TMEM16A/ANO1) expression; goblet cells increased their mucin expression; colonic crypts were characterized by an increase in proliferating epithelial cells; the density of S100-positive glial cells and vimentin-positive fibroblast-like cells was increased as well. Several changes were found in the tunica muscularis : downregulation of α-smooth muscle actin/desmin expression and increased proliferation of smooth muscle cells; increased vimentin expression and proliferative phenotype in myenteric ganglia; reduction of interstitial cells of Cajal (ICCs) density. A pathological remodelling occurs in the colon of 6-OHDA rats. The main changes include: enhanced fibrotic deposition; alterations of the epithelial barrier; activation of mucosal defense; reduction of ICCs. These results indicate that central nigrostriatal denervation is associated with histological changes in the large bowel at mucosal, submucosal and muscular level. These alterations might represent morphological correlates of digestive symptoms in PD. • 6-OHDA-induced central dopaminergic neurodegeneration elicits bowel alterations. • Such changes include colonic inflammation and gut mucosal barrier impairment. • In addition, colonic wall fibrotic remodelling occur in 6-OHDA-rats. • 6-OHDA also elicited a decrease in interstitial cells of Cajal density. • Such alterations could account for digestive symptoms observed in PD patients. [ABSTRACT FROM AUTHOR]